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Abstract:

It has been discovered that pain felt in a given region of the body can
be treated, not by motor point stimulation of muscle in the local region
where pain is felt, but by stimulating muscle spaced from a "nerve of
passage" in a region that is superior (i.e., cranial or upstream toward
the spinal column) to the region where pain is felt. Spinal nerves such
as the intercostal nerves or nerves passing through a nerve plexus, which
comprise trunks that divide by divisions and/or cords into branches,
comprise "nerves of passage."

Claims:

1. A method to reduce and/or relieve pain in a painful region by
stimulating a spinal nerve of passage innervating the painful region with
an electrode inserted into muscle tissue and spaced from the nerve of
passage and upstream of the painful region.

2. A method according to claim 1 wherein the electrode is spaced from the
nerve of passage by a distance of between about one millimeter to about
fifty millimeters.

3. A method to alleviate pain comprising: identifying a tissue region
including skeletal muscle innervated by a spinal nerve of passage
innervating a painful region, placing at least one electrode within the
tissue region spaced from the nerve of passage remote from and upstream
of the painful region, and applying stimulation to the at least one
electrode according to predefined therapeutic stimulation parameters to
affect afferent and/or efferent nerve stimulation within the spinal nerve
of passage and provide therapeutic nerve stimulation to alleviate pain in
the painful region without functional nerve stimulation at a motor point.

4. A method according to claim 3 wherein the nerve of passage includes a
spinal nerve passing through a nerve plexus.

5. A method according to claim 4 wherein the spinal nerve includes a
spinal nerve passing through the brachial plexus.

6. A method according to claim 4 wherein the spinal nerve includes a
spinal nerve passing through the lumbar plexus.

7. A method according to claim 4 wherein the spinal nerve includes a
spinal nerve passing through the sacral plexus.

8. A method according to claim 4 wherein the spinal nerve includes a
spinal nerve passing through the cervical plexus.

9. A method according to claim 3 wherein the spinal nerve includes the
femoral nerve.

10. A method according to claim 3 wherein the spinal nerve includes the
sciatic nerve.

11. A method according to claim 3 wherein the spinal nerve includes an
intercostal nerve.

12. A method according to claim 3 wherein the electrode is spaced from
the nerve of passage by a distance of between about one millimeter to
about fifty millimeters.

13. A system for reducing and/or relieving pain in a painful region
comprising an intramuscular lead, and means for stimulating a spinal
nerve of passage innervating a painful region with the intramuscular lead
inserted into muscle tissue spaced from the nerve of passage and upstream
of the painful region.

14. A system to alleviate pain in a tissue region including skeletal
muscle innervated by a spinal nerve of passage innervating a painful
region, the system comprising at least one electrode sized and configured
for placement within the tissue region spaced from the nerve of passage
remote from and upstream of the painful region, and an electrical pulse
generator for applying stimulation to the at least one electrode
according to predefined therapeutic stimulation parameters to affect
afferent and/or efferent nerve stimulation within the spinal nerve of
passage and provide therapeutic nerve stimulation to alleviate pain in
the painful region without functional nerve stimulation at a motor point.

Description:

RELATED APPLICATIONS

[0001] This application claims the benefit of co-pending U.S. Provisional
Patent Application Ser. No. 61/412,685, filed 11 Nov. 2010, and entitled
"Systems and Methods to Place One or More Leads in Tissue to Electrically
Stimulate Nerves to Treat Pain," which is incorporated herein by
reference.

[0002] This application also claims the benefit and is a
continuation-in-part of co-pending U.S. patent application Ser. No.
12/653,029, filed 7 Dec. 2009, and entitled "Systems and Methods To Place
One or More Leads in Tissue for Providing Functional and/or Therapeutic
Stimulation," which claims the benefit of U.S. Provisional Patent
Application Ser. No. 61/201,030, filed 5 Dec. 2008, and entitled "Systems
and Methods to Place One or More Leads in Tissue for Providing Functional
and/or Therapeutic Stimulation," which are both incorporated herein by
reference.

FIELD OF INVENTION

[0003] This invention relates to systems and methods for placing one or
more leads in tissue to electrically stimulate muscle to treat pain.

BACKGROUND OF THE INVENTION

[0004] The electrical stimulation of nerves, often afferent nerves, to
indirectly affect the stability or performance of a physiological system
can provide functional and/or therapeutic outcomes, and has been used for
activating target nerves to provide therapeutic relief of pain.

[0005] While existing systems and methods can provide remarkable benefits
to individuals requiring therapeutic relief, many issues and the need for
improvements still remain.

[0006] Many techniques have been developed to treat pain, but all of them
are ultimately insufficient.

[0007] Non-narcotic analgesics, such as acetaminophen or non-steroidal
anti-inflammatory drugs (NSAIDS), have relatively minor side effects and
are commonly used for several types of pain. However, they are rarely
sufficient in managing moderate to severe chronic pain (Sherman et al.
1980; Loeser 2001a; Rosenquist and Haider 2008).

[0008] The use of narcotic analgesics, such as N-methyl-D-aspartate (NDMA)
antagonists, has shown only minor success with inconsistent results.
Narcotics carry the risk of addiction and side effects, such as nausea,
confusion, vomiting, hallucinations, drowsiness, dizziness, headache,
agitation, and insomnia.

[0009] Psychological strategies, such as biofeedback and psychotherapy,
may be used as an adjunct to other therapies but are seldom sufficient,
and there are few studies demonstrating efficacy.

[0010] Electrical stimulation systems have been used for the relief of
pain, but widespread use of available systems is limited.

[0011] There exist both external and implantable devices for providing
electrical stimulation to activate nerves and/or muscles to provide
therapeutic relief of pain. These "neurostimulators" are able to provide
treatment and/or therapy to individual portions of the body. The
operation of these devices typically includes the use of an electrode
placed either on the external surface of the skin and/or a surgically
implanted electrode. In most cases, surface electrode(s), cuff-style
electrode(s), paddle-style electrode(s), spinal column electrodes, and/or
percutaneous lead(s) having one or more electrodes may be used to deliver
electrical stimulation to the select portion of the patient's body.

[0012] Transcutaneous electrical nerve stimulation (TENS) has been cleared
by the FDA for treatment of pain. TENS systems are external
neurostimulation devices that use electrodes placed on the skin surface
to activate target nerves below the skin surface. TENS has a low rate of
serious complications, but it also has a relatively low (i.e., less than
25%) long-term rate of success.

[0013] Application of TENS has been used to treat pain successfully, but
it has low long-term patient compliance, because it may cause additional
discomfort by generating cutaneous pain signals due to the electrical
stimulation being applied through the skin, and the overall system is
bulky, cumbersome, and not suited for long-term use (Nashold and Goldner
1975; Sherman 1980; Finsen et al. 1988).

[0014] In addition, several clinical and technical issues associated with
surface electrical stimulation have prevented it from becoming a widely
accepted treatment method. First, stimulation of cutaneous pain receptors
cannot be avoided resulting in stimulation-induced pain that limits
patient tolerance and compliance. Second, electrical stimulation is
delivered at a relatively high frequency to prevent stimulation-induced
pain, which leads to early onset of muscle fatigue in turn preventing
patients from properly using their arm. Third, it is difficult to
stimulate deep nerves and/or muscles with surface electrodes without
stimulating overlying, more superficial nerves and/or muscles resulting
in unwanted stimulation. Finally, clinical skill and intensive patient
training is required to place surface electrodes reliably on a daily
basis and adjust stimulation parameters to provide optimal treatment. The
required daily maintenance and adjustment of a surface electrical
stimulation system is a major burden on both patient and caregiver.

[0015] Spinal cord stimulation (SCS) systems are FDA approved as
implantable neurostimulation devices marketed in the United States for
treatment of pain. Similar to TENS, when SCS evokes paresthesias that
cover the region of pain, it confirms that the location of the electrode
and the stimulus intensity should be sufficient to provide pain relief
and pain relief can be excellent initially, but maintaining sufficient
paresthesia coverage is often a problem as the lead migrates along the
spinal canal (Krainick et al. 1980; Sharan et al. 2002; Buchser and
Thomson 2003).

[0016] Spinal cord stimulation is limited by the invasive procedure and
the decrease in efficacy as the lead migrates. When it can produce
paresthesias in the region of pain, spinal cord stimulation is typically
successful initially in reducing pain, but over time the paresthesia
coverage and pain reduction is often lost as the lead migrates away from
its target (North et al. 1991; Andersen 1997; Loeser 2001a).

[0017] Lead migration is the most common complication for spinal cord
stimulators occurring in up to 45-88% of the cases (North et al. 1991;
Andersen 1997; Spincemaille et al. 2000; Sharan et al. 2002). When the
lead migrates, the active contact moves farther from the target fibers
and loses the ability to generate paresthesias in the target area. SCS
systems attempt to address this problem by using leads with multiple
contacts so that as the lead travels, the next contact in line can be
selected to be the active contact.

[0018] Peripheral nerve stimulation may be effective in reducing pain, but
it previously required specialized surgeons to place cuff- or
paddle-style leads around the nerves in a time consuming procedure.

[0019] These methods of implementation have practical limitations that
prevent widespread use. External systems are too cumbersome, and
implanted spinal cord stimulation systems often have problems of lead
migration along the spinal canal, resulting in either the need for
frequent reprogramming or clinical failure.

[0020] Percutaneous, intramuscular electrical stimulation for the
treatment of post-stroke shoulder pain has been studied as an alternative
to surface electrical stimulation. A feasibility study (Chae, Yu, and
Walker, 2001) and a pilot study (Chae, Yu, and Walker, 2005) showed
significant reduction in pain and no significant adverse events when
using percutaneous, intramuscular electrical stimulation in shoulder
muscles.

[0021] This form of percutaneous, intramuscular electrical stimulation can
be characterized as "motor point" stimulation of muscle. To relieve pain
in the target muscle, the percutaneous lead is placed in the muscle that
is experiencing the pain near the point where a motor nerve enters the
muscle (i.e., the motor point). In "motor point" stimulation of muscle,
the muscle experiencing pain is the same muscle in which the lead is
placed. In "motor point" stimulation of muscle, the pain is felt and
relieved in the area where the lead is located.

SUMMARY OF THE INVENTION

[0022] The invention provides systems and methods for placing one or more
electrodes in tissue for providing electrical stimulation to tissue to
treat pain in a manner unlike prior systems and methods.

[0023] The invention provides systems and methods incorporate a discovery
that pain felt in a given region of the body can be treated, not by motor
point stimulation of muscle in the local region where pain is felt, but
by stimulating muscle close to a "nerve of passage" in a region that is
superior (i.e., cranial or upstream toward the spinal column) to the
region where pain is felt. Neural impulses comprising pain felt in a
given muscle or cutaneous region of the body pass through spinal nerves
that arise from one or more nerve plexuses. The spinal nerves in a nerve
plexus, which comprise trunks that divide by divisions and/or cords into
branches, comprise "nerves of passage." It has been discovered that
applying stimulation in a muscle spaced from a targeted nerve of passage
relieves pain that manifests itself in a region that is inferior (i.e.,
caudal or downstream from the spinal column) from where stimulation is
actually applied.

[0024] Phantom (or amputee) pain is one example of the effectiveness of
"nerves of passage" stimulation, because the area in which phantom pain
is felt does not physically exist. A lead and/or electrode cannot be
physically placed in the muscles that hurt, because those muscles were
amputated. Still, by applying stimulation in a muscle that has not been
amputated spaced from a targeted nerve of passage that, before
amputation, natively innervated the amputated muscles, phantom pain can
be treated.

[0025] Chronic or acute pain in existing, non-amputated muscles can also
be treated by "nerves of passage" stimulation. By applying stimulation in
an existing muscle spaced from a targeted nerve of passage that caudally
innervates the region where chronic or acute pain is manifested, the pain
can be treated.

[0026] In "nerves of passage" stimulation, an electrode can be placed in a
muscle that is conveniently located spaced from a nerve trunk that passes
by the electrode on the way to the painful area. On "nerves of passage"
stimulation, the electrode is placed in a muscle that is not the target
(painful) muscle, but rather a muscle that is upstream from the painful
region, because the proximal muscle presents a convenient and useful
location to place the electrode.

[0027] The systems and methods make possible the treatment of chronic or
acute pain in which muscle contraction cannot be evoked (e.g. in the case
of amputation pain in which the target area has been amputated is no
longer physically present), or other cases of nerve damage either due to
a degenerative diseases or condition such as diabetes of impaired
vascular function (in which the nerves are slowly degenerating,
progressing from the periphery), or due to trauma. The systems and
methods make possible the placement stimulation electrodes in regions
distant from the motor point or region of pain, e.g., where easier access
or more reliable access or a clinician-preferred access be accomplished;
or in situations where the motor nerve point is not available, damaged,
traumatized, or otherwise not desirable; or in situations where it is
desirable to stimulate more than one motor point with a single electrode;
or for cosmetic reasons; or to shorten the distance between the electrode
and its connection with a pulse generator; or to avoid tunneling over a
large area.

[0028] Other features and advantages of the inventions are set forth in
the following specification and attached drawings.

[0040] FIGS. 11A to 11D are views showing a percutaneous lead that can
form a part of a nerve of passage stimulation system.

[0041] FIG. 12 is a view of a package containing a nerve of passage
stimulation system.

[0042] FIGS. 13A/B and 14A/B are representative leads that can form a part
of a nerve of passage stimulation system.

[0043] FIGS. 15A and 15B are schematic anatomic views of a system for
applying nerve of passage stimulation to spinal nerves in the brachial
plexus.

[0044] FIGS. 16A, 16B, and 16C are schematic anatomic views of a system
for applying nerve of passage stimulation to a femoral nerve.

[0045] FIGS. 17A, 17B, and 17C are schematic anatomic views of a system
for applying nerve of passage stimulation to a sciatic/tibial nerve.

[0046] FIGS. 18A and 18B are schematic sectional anatomic views of systems
for applying nerve of passage stimulation to a femoral nerve and a
sciatic/tibial nerve.

[0047] FIGS. 19A, 19B, and 19C are schematic sectional anatomic views of a
system for applying nerve of passage stimulation along a sciatic/tibial
nerve.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0048] Although the disclosure hereof is detailed and exact to enable
those skilled in the art to practice the invention, the physical
embodiments herein disclosed merely exemplify the invention which may be
embodied in other specific structures. While the preferred embodiment has
been described, the details may be changed without departing from the
invention.

[0049] Any elements described herein as singular can be pluralized (i.e.,
anything described as "one" can be more than one). Any species element of
a genus element can have the characteristics or elements of any other
species element of that genus. The described configurations, elements or
complete assemblies and methods and their elements for carrying out the
invention, and variations of aspects of the invention can be combined and
modified with each other in any combination.

I. THE PERIPHERAL NERVOUS SYSTEM

[0050] (Anatomic Overview)

[0051] As generally shown in FIGS. 1A and 1B, the peripheral nervous
system consists of nerve fibers and cell bodies outside the central
nervous system (the brain and the spinal column) that conduct impulses to
or away from the central nervous system. The peripheral nervous system is
made up of nerves (called spinal nerves) that connect the central nervous
system with peripheral structures. The spinal nerves of the peripheral
nervous system arise from the spinal column and exit through
intervertebral foramina in the vertebral column (spine). The afferent, or
sensory, fibers of the peripheral nervous system convey neural impulses
to the central nervous system from the sense organs (e.g., the eyes) and
from sensory receptors in various parts of the body (e.g., the skin,
muscles, etc.). The efferent, or motor, fibers convey neural impulses
from the central nervous system to the effector organs (muscles and
glands).

[0052] The somatic nervous system (SNS) is the part of the peripheral
nervous system associated with the voluntary control of body movements
through the action of skeletal muscles, and with reception of external
stimuli, which helps keep the body in touch with its surroundings (e.g.,
touch, hearing, and sight). The system includes all the neurons connected
with skeletal muscles, skin and sense organs. The somatic nervous system
consists of efferent nerves responsible for sending central nervous
signals for muscle contraction. A somatic nerve is a nerve of the somatic
nervous system.

[0053] A. Spinal Nerves

[0054] A typical spinal nerve arises from the spinal cord by rootlets
which converge to form two nerve roots, the dorsal (sensory) root and the
ventral (motor) root. The dorsal and ventral roots unite into a mixed
nerve trunk that divides into a smaller dorsal (posterior) primary ramus
and a much larger ventral (anterior) primary ramus. The posterior primary
rami serve a column of muscles on either side of the vertebral column,
and a narrow strip of overlying skin. All of the other muscle and skin is
supplied by the anterior primary rami.

[0055] The nerve roots that supply or turn into peripheral nerves can be
generally categorized by the location on the spine where the roots exit
the spinal cord, i.e., as generally shown in FIG. 2A, cervical (generally
in the head/neck, designated C1 to C8), thoracic (generally in
chest/upper back, designated T1 to T12), lumbar (generally in lower back,
designated L1 to L5); and sacral (generally in the pelvis, designated S1
to S5). All peripheral nerves can be traced back (distally toward the
spinal column) to one or more of the spinal nerve roots in either the
cervical, thoracic, lumbar, or sacral regions of the spine. The neural
impulses comprising pain felt in a given muscle or cutaneous region of
the body pass through spinal nerves and (usually) one or more nerve
plexuses. For this reason, the spinal nerves will sometimes be called in
shorthand for the purpose of description "nerves of passage." The spinal
nerves begin as roots at the spine, and can form trunks that divide by
divisions or cords into branches that innervate skin and muscles.

[0056] Spinal nerves have motor fibers and sensory fibers. The motor
fibers innervate certain muscles, while the sensory fibers innervate
certain areas of skin. A skin area innervated by the sensory fibers of a
single nerve root is known as a dermatome. A group of muscles primarily
innervated by the motor fibers of a single nerve root is known as a
myotome. Although slight variations do exist, dermatome and myotome
patterns of distribution are relatively consistent from person to person.

[0057] Each muscle in the body is supplied by a particular level or
segment of the spinal cord and by its corresponding spinal nerve. The
muscle, and its nerve make up a myotome. This is approximately the same
for every person and are as follows:

[0058] C3, 4 and 5 supply the diaphragm (the large muscle between the
chest and the belly that we use to breath).

[0059] C5 also supplies the shoulder muscles and the muscle that we use to
bend our elbow.

[0060] C6 is for bending the wrist back.

[0061] C7 is for straightening the elbow.

[0062] C8 bends the fingers.

[0063] T1 spreads the fingers.

[0064] T1-T12 supplies the chest wall & abdominal muscles.

[0065] L2 bends the hip.

[0066] L3 straightens the knee.

[0067] L4 pulls the foot up.

[0068] L5 wiggles the toes.

[0069] S1 pulls the foot down.

[0070] S3, 4 and 5 supply the bladder, bowel, and sex organs and the anal
and other pelvic muscles.

[0071] Dermatome is a Greek word which literally means "skin cutting". A
dermatome is an area of the skin supplied by nerve fibers originating
from a single dorsal nerve root. The dermatomes are named according to
the spinal nerve which supplies them. The dermatomes form into bands
around the trunk (see FIGS. 2B and 2C), but in the limbs their
organization can be more complex as a result of the dermatomes being
"pulled out" as the limb buds form and develop into the limbs during
embryological development.

[0072] In the diagrams or maps shown in FIGS. 2B and 2C, the boundaries of
dermatomes are usually sharply defined. However, in life there is
considerable overlap of innervation between adjacent dermatomes. Thus, if
there is a loss of afferent nerve function by one spinal nerve sensation
from the region of skin which it supplies is not usually completely lost
as overlap from adjacent spinal nerves occurs; however, there will be a
reduction in sensitivity.

[0073] B. Intercostal Nerves

[0074] The intercostal nerves (see FIGS. 3A, 3B, and 3C) are the anterior
divisions of the thoracic spinal nerves from the thoracic vertebrae T1 to
T11. The intercostal nerves are distributed chiefly to the thoracic
pleura and abdominal peritoneum and differ from the anterior divisions of
the other spinal nerves in that each pursues an independent course
without plexus formation.

[0075] The first two nerves supply fibers to the upper limb in addition to
their thoracic branches; the next four are limited in their distribution
to the parietes of the thorax; the lower five supply the parietes of the
thorax and abdomen. The 7th intercostal nerve terminates at the xyphoid
process, at the lower end of the sternum. The 10th intercostal nerve
terminates at the umbilicus. The twelfth (subcostal) thoracic is
distributed to the abdominal wall and groin.

[0076] Branches of a typical intercostal nerve include the ventral primary
ramus; lateral cutaneous branches that pass beyond the angles of the rubs
and innervate the internal and external intercostal muscles approximately
halfway around the thorax; and the anterior cutaneous branches that
supply the skin on the anterior aspect of the thorax and abdomen.

[0077] C. Spinal Nerve Plexuses

[0078] A nerve plexus is a network of intersecting anterior primary rami.
The sets of anterior primary rami form nerve trunks that ultimately
further divide through divisions and then into cords and then into nerve
branches serving the same area of the body. The nerve branches are mixed,
i.e., they carry both motor and sensory fibers. The branches innervate
the skin, muscle, or other structures. One example of the entry of a
terminal motor nerve branch into muscle is called a motor point.

[0079] As shown in FIGS. 1A and 1B, there are several nerve plexuses in
the body, including (i) the brachial plexus, which serves the chest,
shoulders, arms and hands; (ii) the lumbar plexus, which serves the back,
abdomen, groin, thighs, knees, and calves; (iii) the sacral plexus, which
serves the buttocks, thighs, calves, and feet; (iv) the cervical plexus,
which serves the head, neck and shoulders; and (vi) the solar plexus,
which serves internal organs. The following describes, from an anatomic
perspective, the spinal nerves of passage passing through the various
plexuses, and the muscle and/or skin regions they innervate and where
pain can be felt.

[0080] 1. The Brachial Plexus

[0081] Most nerves in the upper limb arise from the brachial plexus, as
shown in FIGS. 4A and 4B. The brachial plexus begins in the neck
(vertebrae C5 through C7), forms trunks, and extends through divisions
and cords into the axilla (underarm), where nearly all the nerve branches
arise. Primary nerve branches of the brachial plexus include the
musculocutaneous nerve; the median nerve; the ulnar nerve; the axillary
nerve; and the radial nerve.

[0082] a. The Musculocutaneous Nerve

[0083] The musculocutaneous nerve arises from the lateral cord of the
brachial plexus. Its fibers are derived from cervical vertebrae C5, C6.
The musculocutaneous nerve penetrates the coracobrachialis muscle and
passes obliquely between the biceps brachii and the brachialis, to the
lateral side of the arm. Just above the elbow, the musculocutaneous nerve
pierces the deep fascia lateral to the tendon of the biceps brachii
continues into the forearm as the lateral antebrachial cutaneous nerve.
In its course through the arm, the musculocutaneous nerve innervates the
coracobrachialis, biceps brachii, and the greater part of the brachialis.

[0084] b. The Median Nerve

[0085] The median nerve is formed from parts of the medial and lateral
cords of the brachial plexus, and continues down the arm to enter the
forearm with the brachial artery. It originates from the brachial plexus
with roots from cervical vertebrae C5, C6, C7 and thoracic vertebra T1.
The median nerve innervates all of the flexors in the forearm, except
flexor carpi ulnaris and that part of flexor digitorum profundus that
supplies the medial two digits. The latter two muscles are supplied by
the ulnar nerve of the brachial plexus. The median nerve is the only
nerve that passes through the carpal tunnel, where it may be compressed
to cause carpal tunnel syndrome.

[0088] In the hand, the median nerve supplies motor innervation to the 1st
and 2nd lumbrical muscles. It also supplies the muscles of the thenar
eminence by a recurrent thenar branch. The rest of the intrinsic muscles
of the hand are supplied by the ulnar nerve of the brachial plexus.

[0089] The median nerve innervates the skin of the palmar side of the
thumb, the index and middle finger, half the ring finger, and the nail
bed of these fingers. The lateral part of the palm is supplied by the
palmar cutaneous branch of the median nerve, which leaves the nerve
proximal to the wrist creases. The palmar cutaneous branch travels in a
separate fascial groove adjacent to the flexor carpi radialis and then
superficial to the flexor retinaculum. It is therefore spared in carpal
tunnel syndrome.

[0090] c. The Ulnar Nerve

[0091] The ulnar nerve comes from the medial cord of the brachial plexus,
and descends on the posteromedial aspect of the humerus. It goes behind
the medial epicondyle, through the cubital tunnel at the elbow (where it
is vulnerable to injury for a few centimeters, just above the joint). One
method of injuring the nerve is to strike the medial epicondyle of the
humerus from posteriorly, or inferiorly with the elbow flexed. The ulnar
nerve is trapped between the bone and the overlying skin at this point.
This is commonly referred to as hitting one's "funny bone."

[0092] The ulnar nerve is the largest nerve not protected by muscle or
bone in the human body. The ulnar nerve is the only unprotected nerve
that does not serve a purely sensory function. The ulnar nerve is
directly connected to the little finger, and the adjacent half of the
ring finger, supplying the palmar side of these fingers, including both
front and back of the tips, as far back as the fingernail beds.

[0094] The ulnar nerve also provides sensory innervation to the fifth
digit and the medial half of the fourth digit, and the corresponding part
of the palm. The Palmar branch of ulnar nerve supplies cutaneous
innervation to the anterior skin and nails. The dorsal branch of ulnar
nerve supplies cutaneous innervation to the posterior skin (except the
nails).

[0095] d. The Axillary Nerve

[0096] The axillary nerve comes off the posterior cord of the brachial
plexus at the level of the axilla (armpit) and carries nerve fibers from
vertebrae C5 and C6. The axillary nerve travels through the quadrangular
space with the posterior circumflex humeral artery and vein. It supplies
two muscles: the deltoid (a muscle of the shoulder), and the teres minor
(one of the rotator cuff muscles). The axillary nerve also carries
sensory information from the shoulder joint, as well as from the skin
covering the inferior region of the deltoid muscle, i.e., the "regimental
badge" area (which is innervated by the superior lateral cutaneous nerve
branch of the axillary nerve). When the axillary nerve splits off from
the posterior cord, the continuation of the cord is the radial nerve.

[0097] e. The Radial Nerve

[0098] The radial nerve supplies the upper limb, supplying the triceps
brachii muscle of the arm, as well as all twelve muscles in the posterior
osteofascial compartment of the forearm, as well as the associated joints
and overlying skin. The radial nerve originates from the posterior cord
of the brachial plexus with roots from cervical vertebrae C5, C6, C7, C8
and thoracic vertebra T1.

[0099] Cutaneous innervation is provided by the following nerves: (i)
posterior cutaneous nerve of arm (originates in axilla); (ii) inferior
lateral cutaneous nerve of arm (originates in arm); and (iii) posterior
cutaneous nerve of forearm (originates in arm). The superficial branch of
the radial nerve provides sensory innervation to much of the back of the
hand, including the web of skin between the thumb and index finger.

[0102] The radial nerve (and its deep branch) provides motor innervation
to the muscles in the posterior compartment of the arm and forearm, which
are mostly extensors.

[0103] 2. Sacral and Lumbar Plexuses

[0104] The lumbar plexus (see FIG. 5) is a nervous plexus in the lumbar
region of the body and forms part of the lumbosacral plexus. It is formed
by the ventral divisions of the first four lumbar nerves (L1-L4) and from
contributions of the subcostal thoracic nerve (T12), which is the last
(most inferior) thoracic nerve.

[0105] Additionally, the ventral rami of sacral vertebrae S2 and S3 nerves
emerge between digitations of the piriformis and coccygeus nuscles. The
descending part of the lumbar vertebrae L4 nerve unites with the ventral
ramus of the lumbar vertebrae L5 nerve to form a thick, cordlike
lumbosacral trunk. The lumbosacral trunk joins the sacral plexus (see
FIG. 6). The main nerves of the lower limbs arise from the lumbar and
sacral plexuses.

[0106] a. Nerves of the Sacral Plexus

[0107] The sacral plexus provides motor and sensory nerves for the
posterior thigh, most of the lower leg, and the entire foot.

[0108] (1) The Sciatic Nerve

[0109] As shown in FIGS. 1A and 6, the sciatic nerve (also known as the
ischiatic nerve) arises from the sacral plexus. It is the longest and
widest single nerve in the human body. It begins in the lower back and
runs through the buttock and down the lower limb. The sciatic nerve
supplies nearly the whole of the skin of the leg, the muscles of the back
of the thigh, and those of the leg and foot. It is derived from spinal
nerves L4 through S3. It contains fibers from both the anterior and
posterior divisions of the lumbosacral plexus.

[0110] The nerve gives off articular and muscular branches. The articular
branches (rami articulares) arise from the upper part of the nerve and
supply the hip-joint, perforating the posterior part of its capsule; they
are sometimes derived from the sacral plexus. The muscular branches (rami
musculares) innervate the following muscles of the lower limb: biceps
femoris, semitendinosus, semimembranosus, and adductor magnus. The nerve
to the short head of the biceps femoris comes from the common peroneal
part of the sciatic, while the other muscular branches arise from the
tibial portion, as may be seen in those cases where there is a high
division of the sciatic nerve.

[0111] The muscular branch of the sciatic nerve eventually gives off the
tibial nerve (shown in FIG. 1A) and common peroneal nerve (also shown in
FIG. 1A), which innervates the muscles of the (lower) leg. The tibial
nerve goes on to innervate all muscles of the foot except the extensor
digitorum brevis (which is innervated by the peroneal nerve).

[0112] b. Nerves of the Lumbar Plexus

[0113] The lumbar plexus (see FIG. 5) provides motor, sensory, and
autonomic fibres to gluteal and inguinal regions and to the lower
extremities. The gluteal muscles are the three muscles that make up the
buttocks: the gluteus maximus muscle, gluteus medius muscle and gluteus
minimus muscle. The inguinal region is situated in the groin or in either
of the lowest lateral regions of the abdomen.

[0114] (1) The Iliohypogastric Nerve

[0115] The iliohypogastric nerve (see FIG. 5) runs anterior to the psoas
major on its proximal lateral border to run laterally and obliquely on
the anterior side of quadratus lumborum. Lateral to this muscle, it
pierces the transversus abdominis to run above the iliac crest between
that muscle and abdominal internal oblique. It gives off several motor
branches to these muscles and a sensory branch to the skin of the lateral
hip. Its terminal branch then runs parallel to the inguinal ligament to
exit the aponeurosis of the abdominal external oblique above the external
inguinal ring where it supplies the skin above the inguinal ligament
(i.e. the hypogastric region) with the anterior cutaneous branch.

[0116] (2) The Ilioinguinal Nerve

[0117] The ilioinguinal nerve (see FIG. 5) closely follows the
iliohypogastric nerve on the quadratus lumborum, but then passes below it
to run at the level of the iliac crest. It pierces the lateral abdominal
wall and runs medially at the level of the inguinal ligament where it
supplies motor branches to both transversus abdominis and sensory
branches through the external inguinal ring to the skin over the pubic
symphysis and the lateral aspect of the labia majora or scrotum.

[0118] (3) The Genitofemoral Nerve

[0119] The genitofemoral nerve (see FIG. 5) pierces psoas major anteriorly
below the former two nerves to immediately split into two branches that
run downward on the anterior side of the muscle. The lateral femoral
branch is purely sensory. It pierces the vascular lacuna near the
saphenous hiatus and supplies the skin below the inguinal ligament (i.e.
proximal, lateral aspect of femoral triangle). The genital branch differs
in males and females. In males it runs in the spermatic cord and in
females in the inguinal canal together with the teres uteri ligament. It
then sends sensory branches to the scrotal skin in males and the labia
majora in females. In males it supplies motor innervation to the
cremaster.

[0120] (4) The Lateral Cutaneous Femoral Nerve

[0121] The lateral cutaneous femoral nerve (see FIG. 5) pierces psoas
major on its lateral side and runs obliquely downward below the iliac
fascia. Medial to the anterior superior iliac spine it leaves the pelvic
area through the lateral muscular lacuna. In the thigh it briefly passes
under the fascia lata before it breaches the fascia and supplies the skin
of the anterior thigh.

[0122] (5) The Obturator Nerve

[0123] The obturator nerve (see FIG. 5) leaves the lumbar plexus and
descends behind psoas major on it medial side, then follows the linea
terminalis and exits through the obturator canal. In the thigh, it sends
motor branches to obturator externus before dividing into an anterior and
a posterior branch, both of which continues distally. These branches are
separated by adductor brevis and supply all thigh adductors with motor
innervation: pectineus, adductor longus, adductor brevis, adductor
magnus, adductor minimus, and gracilis. The anterior branch contributes a
terminal, sensory branch which passes along the anterior border of
gracilis and supplies the skin on the medial, distal part of the thigh.

[0124] (6) The Femoral Nerve

[0125] The femoral nerve (see FIG. 5 and also FIG. 16A) is the largest and
longest nerve of the lumbar plexus. It gives motor innervation to
iliopsoas, pectineus, sartorius, and quadriceps femoris; and sensory
innervation to the anterior thigh, posterior lower leg, and hindfoot. It
runs in a groove between psoas major and iliacus giving off branches to
both muscles. In the thigh it divides into numerous sensory and muscular
branches and the saphenous nerve, its long sensory terminal branch which
continues down to the foot.

[0126] 3. The Cervical Plexus

[0127] The cervical plexus (see FIG. 7) is a plexus of the ventral rami of
the first four cervical spinal nerves which are located from C1 to C4
cervical segment in the neck. They are located laterally to the
transverse processes between prevertebral muscles from the medial side
and vertebral (m. scalenus, m. levator scapulae, m. splenius cervicis)
from lateral side. Here there is anastomosis with accessory nerve,
hypoglossal nerve and sympathetic trunk.

[0128] The cervical plexus is located in the neck, deep to
sternocleidomastoid. Nerves formed from the cervical plexus innervate the
back of the head, as well as some neck muscles. The branches of the
cervical plexus emerge from the posterior triangle at the nerve point, a
point which lies midway on the posterior border of the
Sternocleidomastoid.

[0129] The nerves formed by the cervical plexus supply the back of the
head, the neck and the shoulders. The face is supplied by a cranial
nerve, the trigeminal nerve. The upper four posterior primary rami are
larger than the anterior primary rami. The C1 posterior primary ramus
does not usually supply the skin. The C2 posterior primary ramus forms
the greater occipital nerve which supplies the posterior scalp. The upper
four anterior primary rami form the cervical plexus. The cervical plexus
supplies the skin over the anterior and lateral neck to just below the
clavicle. The plexus also supplies the muscles of the neck including the
scalenes, the strap muscles, and the diaphragm.

[0130] The cervical plexus has two types of branches: cutaneous and
muscular.

[0131] The cutaneous branches include the lesser occipital nerve, which
innervates lateral part of occipital region (C2 nerve only); the great
auricular nerve, which innervates skin near concha auricle and external
acoustic meatus (C2 and C3 nerves); the transverse cervical nerve, which
innervates anterior region of neck (C2 and C3 nerves); and the
supraclavicular nerves, which innervate region of suprascapularis,
shoulder, and upper thoracic region (C3, C4 Nerves)

[0134] The solar plexus (see FIG. 8) is a dense cluster of nerve cells and
supporting tissue, located behind the stomach in the region of the celiac
artery just below the diaphragm. It is also known as the celiac plexus.
Rich in ganglia and interconnected neurons, the solar plexus is the
largest autonomic nerve center in the abdominal cavity. Through branches
it controls many vital functions such as adrenal secretion and intestinal
contraction.

[0135] Derived from the solar plexus are the phrenic plexus (producing
contractions of the diaphragm, and providing sensory innervation for many
components of the mediastinum and pleura); the renal plexuses (affecting
renal function); the spermatic plexus (affecting function of the testis);
as well as the gastric plexus; the hepatic plexus; the splenic plexus;
the superior mesenteric plexus; and the aortic plexus.

II. THE SYSTEM

[0136] The various aspects of the invention will be described in
connection with the placement of one or more leads 12 having one or more
electrodes 14, in muscle, and in electrical proximity but away from
nerves, for improved recruitment of targeted nerves for therapeutic
purposes, such as for the treatment of pain. That is because the features
and advantages that arise due to the invention are well suited to this
purpose. It is to be appreciated that regions of pain can include any or
all portions of the body, including arms and legs in both humans and
animals.

[0137] A. Stimulation of Nerves of Passage

[0138] FIG. 9 shows a typical "motor point" system and method for
stimulating a nerve or muscle A by placing a lead 12(A) with its
electrode 14(A) close to motor point A. As previously described, a motor
point A is the location where the innervating spinal nerve enters the
muscle. At that location, the electrical stimulation intensity required
to elicit a full contraction is at the minimum. Any other location in the
muscle would require more stimulation intensity to elicit the same muscle
contraction.

[0139] FIG. 10 shows a "nerves of passage" system and method, that is
unlike the "motor point" system and method shown in FIG. 9, and which
incorporates the features of the invention. As shown in FIG. 10, the
system and method identifies a region where there is a local
manifestation of pain. The region of pain can comprise, e.g., skin, bone,
a joint, or muscle. The system and method identify one or more spinal
nerves that are located anatomically upstream or cranial to the region
where pain is manifested, through which neural impulses comprising the
pain pass. A given spinal nerve that is identified can comprise a nerve
trunk located in a nerve plexus, or a divisions and/or a cord of a nerve
trunk, or a nerve branch, provided that it is upstream or cranial of
where the nerve innervates the region affected by the pain. The given
spinal nerve can be identified by medical professionals using textbooks
of human anatomy along with their knowledge of the site and the nature of
the pain or injury, as well as by physical manipulated and/or imaging,
e.g., by ultrasound, fluoroscopy, or X-ray examination, of the region
where pain is manifested. A desired criteria of the selection includes
identifying the location of muscle in electrical proximity to but spaced
away from the nerve or passage, which muscle can be accessed by placement
of one or more stimulation electrodes, aided if necessary by ultrasonic
or electro-location techniques. The nerve identified comprises a targeted
"nerve of passage." The muscle identified comprises the "targeted
muscle." In a preferred embodiment, the electrodes are percutaneously
inserted using percutaneous leads.

[0140] The system and method place the one or more leads 12(B) with its
electrode 14(B) in the targeted muscle in electrical proximity to but
spaced away from the targeted nerve of passage. The system and method
apply electrical stimulation through the one or more stimulation
electrodes to electrically activate or recruit the targeted nerve of
passage that conveys the neural impulses comprising the pain to the
spinal column.

[0141] The system and method can apply electrical stimulation to nerves of
passage throughout the body. For example, the nerves of passage can
comprise one or more spinal nerves in the brachial plexus, to treat pain
in the chest, shoulders, arms and hands; and/or one or more spinal nerves
in the lumbar plexus, to treat pain in the back, abdomen, groin, thighs,
knees, and calves; and/or one or more spinal nerves in the sacral plexus,
to treat pain in the buttocks, thighs, calves, and feet; and/or one or
more spinal nerves in the cervical plexus, to treat pain in the head,
neck and shoulders; and/or one or more spinal nerves in the solar plexus,
to treat pain or dysfunction in internal organs.

[0142] For example, if the pinky finger hurts, the system and method can
identify and stimulate the ulnar nerve at a location that it is upstream
or cranial of where the nerve innervates the muscle or skin of the pinky
finger, e.g., in the palm of the hand, forearm, and/or upper arm. If
electrical stimulation activates the target nerve of passage sufficiently
at the correct intensity, then the patient will feel a comfortable
tingling sensation called a paresthesia in the same region as their pain,
which overlap with the region of pain and/or otherwise reduce pain.

[0143] It is to be appreciated that the sensation could be described with
other words such as buzzing, thumping, etc. Evoking paresthesias in the
region of pain confirms correct lead placement and indicates stimulus
intensity is sufficient to reduce pain. Inserting a lead 12
percutaneously allows the lead 12 to be placed quickly and easily, and
placing the lead 12 in a peripheral location, i.e., muscle, where it is
less likely to be dislodged, addresses the lead migration problems of
spinal cord stimulation that result in decreased paresthesia coverage,
decreased pain relief, and the need for frequent patient visits for
reprogramming.

[0144] Placing the lead 12 percutaneously in muscle in electrical
proximity to but spaced away from the targeted nerve of passage minimize
complications related to lead placement and movement. In a percutaneous
system, an electrode lead 12, such as a coiled fine wire electrode lead
may be used because it is minimally-invasive and well suited for
placement in proximity to a nerve of passage. The lead can be sized and
configured to withstand mechanical forces and resist migration during
long-term use, particularly in flexible regions of the body, such as the
shoulder, elbow, and knee.

[0145] B. The Lead

[0146] As FIG. 11A shows, the electrode lead can comprise, e.g., a fine
wire electrode 14, paddle electrode, intramuscular electrode, or
general-purpose electrode, inserted via a needle introducer 30 or
surgically implanted in proximity of a targeted nerve of passage. Once
proper placement is confirmed, the needle introducer 30 may be withdrawn
(as FIGS. 11B and 11C show), leaving the electrode in place. Stimulation
may also be applied through a penetrating electrode, such as an electrode
array comprised of any number (i.e., one or more) of needle-like
electrodes that are inserted into the target site. In both cases, the
lead may placed using a needle-like introducer 30, allowing the
lead/electrode placement to be minimally invasive.

[0147] In a representative embodiment, the lead 12 comprises a thin,
flexible component made of a metal and/or polymer material. By "thin," it
is contemplated that the lead should not be greater than about 0.75 mm
(0.030 inch) in diameter.

[0148] The lead 12 can comprise, e.g., one or more coiled metal wires with
in an open or flexible elastomer core. The wire can be insulated, e.g.,
with a biocompatible polymer film, such as polyfluorocarbon, polyimide,
or parylene. The lead is desirably coated with a textured, bacteriostatic
material, which helps to stabilize the lead in a way that still permits
easy removal at a later date and increases tolerance.

[0149] The lead 12 may be electrically insulated everywhere except at one
(monopolar), or two (bipolar), or three (tripolar), for example,
conduction locations near its distal tip. Each of the conduction
locations may be connected to one or more conductors that run the length
of the lead and lead extension 16 (see FIG. 11C), proving electrical
continuity from the conduction location through the lead 12 to an
external pulse generator or stimulator 28 (see FIG. 11C) or an implanted
pulse generator or stimulator 28 (see FIG. 11D).

[0150] The conduction location or electrode 14 may comprise a de-insulated
area of an otherwise insulated conductor that runs the length of an
entirely insulated electrode. The de-insulated conduction region of the
conductor can be formed differently, e.g., it can be wound with a
different pitch, or wound with a larger or smaller diameter, or molded to
a different dimension. The conduction location or the electrode 14 may
comprise a separate material (e.g., metal or a conductive polymer)
exposed to the body tissue to which the conductor of the wire is bonded.

[0151] The lead 12 is desirably provided in a sterile package 62 (see FIG.
12), and may be pre-loaded in the introducer needle 30. The package 62
can take various forms and the arrangement and contents of the package
62. As shown in FIG. 12, the package 62 comprises a sterile, wrapped
assembly. The package 62 includes an interior tray made, e.g., from die
cut cardboard, plastic sheet, or thermo-formed plastic material, which
hold the contents. The package 62 also desirably includes instructions
for use 58 for using the contents of the package to carry out the lead
location and placement procedures, as will be described inb greater
detail below.

[0152] The lead 12 desirably possess mechanical properties in terms of
flexibility and fatigue life that provide an operating life free of
mechanical and/or electrical failure, taking into account the dynamics of
the surrounding tissue (i.e., stretching, bending, pushing, pulling,
crushing, etc.). The material of the electrode desirably discourages the
in-growth of connective tissue along its length, so as not to inhibit its
withdrawal at the end of its use. However, it may be desirable to
encourage the in-growth of connective tissue at the distal tip of the
electrode, to enhance its anchoring in tissue.

[0153] One embodiment of the lead 12 shown in FIG. 13A may comprise a
minimally invasive coiled fine wire lead 12 and electrode 14. The
electrode 14 may also include, at its distal tip, an anchoring element
48. In the illustrated embodiment, the anchoring element 48 takes the
form of a simple barb or bend (see also FIG. 11C).

[0154] The anchoring element 48 is sized and configured so that, when in
contact with tissue, it takes purchase in tissue, to resist dislodgement
or migration of the electrode out of the correct location in the
surrounding tissue.

[0155] Desirably, the anchoring element 48 is prevented from fully
engaging body tissue until after the electrode 14 has been correctly
located and deployed.

[0156] An alternative embodiment of an electrode lead 12 shown in FIGS.
14A and 14B, may also include, at or near its distal tip or region, one
or more anchoring element(s) 70. In the illustrated embodiment, the
anchoring element 70 takes the form of an array of shovel-like paddles or
scallops 76 proximal to the proximal-most electrode 14 (although a paddle
76 or paddles could also be proximal to the distal most electrode 14, or
could also be distal to the distal most electrode 14). The paddles 76 as
shown are sized and configured so they will not cut or score the
surrounding tissue. The anchoring element 70 is sized and configured so
that, when in contact with tissue, it takes purchase in tissue, to resist
dislodgement or migration of the electrode out of the correct location in
the surrounding tissue (e.g., muscle 54). Desirably, the anchoring
element 70 is prevented from fully engaging body tissue until after the
electrode 14 has been deployed. The electrode is not deployed until after
it has been correctly located during the implantation (lead placement)
process, as previously described. In addition, the lead 12 may include
one or more ink markings 74, 75 (shown in FIG. 14A) to aid the physician
in its proper placement.

[0158] In all cases, the lead may exit through the skin and connect with
one or more external stimulators 28 (shown in FIG. 11C), or the lead(s)
may be routed subcutaneously to one or more implanted pulse generators 28
(shown in FIG. 11D), or they may be connected as needed to internal and
external coils for RF (Radio Frequency) wireless telemetry communications
or an inductively coupled telemetry to control the implanted pulse
generator. As shown in FIG. 11D, the implanted pulse generator 28 may be
located some distance (remote) from the electrode 14, or an implanted
pulse generator may be integrated with an electrode(s) (not shown),
eliminating the need to route the lead subcutaneously to the implanted
pulse generator.

[0159] The introducer 30 (see FIG. 11A) may be insulated along the length
of the shaft, except for those areas that correspond with the exposed
conduction surfaces of the electrode 14 housed inside the introducer 30.
These surfaces on the outside of the introducer 30 are electrically
isolated from each other and from the shaft of the introducer 30. These
surfaces may be electrically connected to a connector 64 at the end of
the introducer body (see FIG. 11A). This allows connection to an external
stimulator 28 (shown in FIG. 11A) during the implantation process.
Applying stimulating current through the outside surfaces of the
introducer 30 provides a close approximation to the response that the
electrode 14 will provide when it is deployed at the current location of
the introducer 30.

[0160] The introducer 30 may be sized and configured to be bent by hand
prior to its insertion through the skin. This will allow the physician to
place lead 12 in a location that is not in an unobstructed straight line
with the insertion site. The construction and materials of the introducer
30 allow bending without interfering with the deployment of the lead 12
and withdrawal of the introducer 30, leaving the lead 12 in the tissue.

[0161] C. Insertion of the Lead

[0162] Representative lead insertion techniques will now be described to
place an electrode lead 12 in a desired location in muscle in electrical
proximity to but spaced away from a nerve of passage. It is this lead
placement that makes possible the stimulation of the targeted nerve or
nerves of passage with a single lead 12 to provide pain relief.

[0163] Instructions for use 58 (see FIG. 12) can direct use of system and
method for the placement of a lead 12 in muscle in electrical proximity
to but spaced away from the nerve or nerves of passage for improved
recruitment of target nerves, e.g., with the placement of one or more
leads 12. The instructions for use may include instructions for placing a
lead 12 for the activation of the targeted nerve of passage in a system
for the relief of pain, for example. The instructions for use may also
include instructions for recording stimulus parameters, including
intensity associated with a first sensation of stimulation, a first
noticeable muscle contraction, and a maximum tolerable contraction at
multiple locations, which can be used to aid in determining desired
stimulation parameters for optimal stimulation.

[0164] The instructions 58 can, of course vary. The instructions 58 may be
physically present in a kits holding the lead 12 (as FIG. 12 shows), but
can also be supplied separately. The instructions 58 can be embodied in
separate instruction manuals, or in video or audio tapes, CD's, and
DVD's. The instructions 58 for use can also be available through an
internet web page.

[0165] To determine the optimal placement for the lead 12, test
stimulation may be delivered through needle electrodes, and muscle
responses may be observed. The motor point(s) of the target muscle(s) may
be located first in order to confirm that the muscles are innervated.
Needle electrodes may be used because they can be easily repositioned
until the optimal location to deliver stimulation is determined.

[0166] At least one lead(s) may be placed in muscle tissue near a targeted
nerve of passage. The lead may be inserted via the introducer 30 in
conventional fashion, which may be similar in size and shape to a
hypodermic needle. The introducer 30 may be any size. In a preferred
embodiment, the introducer 30 may range in size from 17 gauge to 26
gauge. Prior to inserting the introducer 30, the insertion site may be
cleaned with a disinfectant (e.g. Betadine, 2% Chlorhexidine/80% alcohol,
10% povidone-iodine, or similar agent). A local anesthetic(s) may be
administered topically and/or subcutaneously to the area in which the
electrode and/or introducer will be inserted.

[0167] The position of the electrodes may be checked by imaging
techniques, such as ultrasound, fluoroscopy, or X-rays. Following
placement of the lead(s), the portion of the leads which exit the skin
may be secured to the skin using covering bandages and/or adhesives.

[0168] Electrical stimulation may be applied to the targeted nerve of
passage during and after placement of the electrode to determine whether
stimulation of the targeted nerve of passage can generate comfortable
sensations or paresthesias that overlap with the region of pain and/or
reduce pain. The pain may be perceived to be contained within a specific
part(s) of the body and/or it may be perceived to be located outside of
the body, as may be the case in persons with amputations who have phantom
pain or pain in the amputated (or phantom) limb(s).

[0169] In a percutaneous system 10 (as FIGS. 11A to 11D show, the lead 12
may be percutaneously placed near the targeted nerve of passage and exit
at a skin puncture site 16. A trial or screening test may be conducted in
a clinical setting (e.g. an office of a clinician, a laboratory, a
procedure room, an operating room, etc.). During the trial, the lead is
coupled to an external pulse generator 28 and temporary percutaneous
and/or surface return electrodes, to confirm paresthesia coverage and/or
pain relief of the painful areas.

[0170] If the clinical screening test is successful, the patient may
proceed to a home-trial coupled to an external pulse generator 28 (as
shown in FIG. 11C) and temporary percutaneous and/or surface return
electrodes, to determine if pain relief can be sustained in the home
environment. The trial period may range from minutes to hours to days to
weeks to months. The preferred trial period may be between 3 and 21 days.

[0171] If either the screening test or home trial is unsuccessful, the
lead 12 may be quickly and easily removed.

[0172] However, if the screening test and/or home-trial are successful,
the patient's percutaneous system may be converted into a fully implanted
system (as shown in FIG. 11D) by replacing the external pulse generator
with an implantable pulse generator 28 (the housing of which serves as a
return electrode).

[0173] Alternatively, it may be preferred to use a percutaneous system(s)
as a therapy without proceeding to a fully implantable system. It is also
to be appreciated that a home-trial is not a requirement for either the
percutaneous system or a fully implanted system.

[0174] The duration of therapy for a percutaneous system may range from
minutes to days to weeks to months to multiple years, but a preferred
embodiment includes a duration ranging from 1 to 12 weeks.

[0175] Electrical stimulation is applied between the lead and return
electrodes (uni-polar mode). Regulated current is the preferred type of
stimulation, but other type(s) of stimulation (e.g. non-regulated current
such as voltage-regulated) may also be used. Multiple types of electrodes
may be used, such as surface, percutaneous, and/or implantable
electrodes. The surface electrodes may be a standard shape or they may be
tailored if needed to fit the contour of the skin.

[0176] In a preferred embodiment of a percutaneous system, the surface
electrode(s) may serve as the anode(s) (or return electrode(s)), but the
surface electrode(s) may be used as the cathode(s) (active electrode(s))
if necessary. When serving as a return electrod(e), the location of the
electrode(s) is not critical and may be positioned anywhere in the
general vicinity, provided that the current path does not cross the
heart. If a surface electrode(s) serves as an active electrode(s), it
(they) may be positioned near the target stimulation area(s) (e.g. on the
skin surface over the target nerve or passage).

[0177] The electrode lead may be placed via multiple types of approaches.
In one embodiment, the approach may be similar needle placement for
electromyography (EMG).

[0178] For example (as shown in FIG. 15A), if the targeted nerve of
passage includes nerves of the brachial plexus, the approach can include:

[0179] 1) Place the patient in a comfortable and/or appropriate position
with head turned away from the lead insertion site.

[0180] 2) Prepare the lead insertion site with antiseptic and local
subcutaneous anesthetic (e.g., 2% lidocaine).

[0181] 3) Locate the site of skin puncture with appropriate landmarks,
such as the clavical, coracoid process, and axilla, as necessary.

[0182] 4) Insert a sterile percutaneous electrode lead 12 preloaded in the
introducer needle 30 at a predetermined angle based on landmarks used.

[0183] 5) Place a surface stimulation return electrode in proximity of the
area in which the percutaneous lead 12 has been placed. Test stimulation
will be applied to the lead 12, with the surface electrode providing a
return path. The surface electrode may be placed adjacent to the lead.
Its position is not critical to the therapy and it can be moved
throughout the therapy to reduce the risk of skin irritation.

[0184] 6) Couple the lead 12 to the external pulse generator 28 and to the
return electrode. Set the desired stimulation parameters. Test
stimulation may be delivered using a current-regulated pulse generator,
for example. The external pulse generator 28 may be programmed to 4 mA,
100 μs, 100 Hz, and an on-off duty cycle of 0.25 sec., as a
non-limiting example.

[0185] 7) Advance the introducer slowly until the subject reports the
first evoked sensation in the region experiencing pain. Progressively
reduce the stimulus amplitude and advance the introducer more slowly
until the sensation can be evoked in the painful region at a
predetermined stimulus amplitude (e.g., 1 mA). Stop the advancement of
the introducer, and increase the stimulus amplitude in small increments
(e.g., 0.1 mA) until the stimulation-evoked tingling sensation
(paresthesia) expands to overlay the entire region of pain.

[0186] 8) Withdraw the introducer 30, leaving the percutaneous lead 12 in
proximity but away from the target nerve (see FIG. 15B).

[0187] 9) Cover the percutaneous exit site and lead 12 with a bandage. A
bandage may also be used to secure the external portion of the lead 12
(or an extension cable used to couple the lead 12 to the external pulse
generator) to the skin. It is expected the length of time to place the
lead 12 to be less than 10 minutes, although the process may be shorter
or longer.

[0188] 10) Vary the stimulus amplitude in small steps (e.g., 0.1-0.5 mA)
to determine the thresholds at which stimulation evokes first sensation
(TSEN), sensation (paresthesia) superimposed on the region of pain
(TSUP), muscle twitch (TMUS) of the target muscle (innervated
or not innervated by the target nerve), and maximum comfortable sensation
(TMAX). Query the subject at each stimulus amplitude to determine
sensation level, and visually monitor muscle response. Record the
results.

[0189] 11) It is possible that stimulation intensity may need to be
increased slightly during the process due to causes such as habituation
or the subject becoming accustomed to sensation, but the need for
increased intensity is unlikely and usually only occurs after several
days to weeks to months as the tissue encapsulates and the subject
accommodates to stimulation. It is to be appreciated that the need for
increased intensity could happen at any time, even years out, which would
likely be due to either lead migration or habituation, but may also be
due reasons ranging from nerve damage to plasticity/reorganization in the
central nervous system.

[0190] 12) If paresthesias cannot be evoked with the initial lead
placement, redirect the introducer 30.

[0191] 13) If sensations still cannot be evoked in a given subject, then
the muscle twitch response of the muscle innervated or not innervated by
the target nerve may be used to guide lead placement and then increase
stimulus intensity until sufficient paresthesias are elicited in the
painful region. Minimal muscle contraction may be acceptable if it is
well tolerated by the patient in exchange for significant pain relief and
if it does not lead to additional discomfort or fatigue.

[0192] 14) If stimulation evokes muscle contraction at a lower stimulus
threshold than paresthesia (e.g. if TMUS≦TSUP) and
contraction leads to discomfort, then a lower stimulus frequency (e.g.,
12 Hz) may be used because low frequencies (e.g., 4-20 Hz) have been
shown to minimize discomfort due to muscle contraction and provide
>50% relief of shoulder pain in stroke patients while still inhibiting
transmission of pain signals in the central nervous system in animals. If
continued muscle contraction leads to pain due to fatigue, change the
duty cycle, using parameters shown to reduce muscle fatigue and related
discomfort in the upper extremity (e.g. 5 s ramp up, 10 s on, 5 s ramp
down, 10 s off).

[0193] 15) If stimulation fails to elicit paresthesia in all areas of
pain, then a second percutaneous lead (not shown) may need to be placed
to stimulate the nerves that are not activated by the first lead 12.

[0194] 16)

[0195] If stimulation is successful, i.e., if the screening test and/or
home-trial are successful, the patient's percutaneous system (see FIG. 1)
may be converted into a fully implanted system by replacing the external
pulse generator 28 with an implantable pulse generator that is implanted
in a convenient area (see FIG. 11D) (e.g., in a subcutaneous pocket over
the hip or in the subclavicular area). In one embodiment, the electrode
lead 12 used in the screening test and/or home-trial may be totally
removed and discarded, and a new completely implantable lead may be
tunneled subcutaneously and coupled to the implantable pulse generator.
In an alternative embodiment, a two part lead may be incorporated in the
screening test and/or home-trial where the implantable part is completely
under the skin and connected to a percutaneous connector (i.e.,
extension) that can be discarded after removal. The implantable part may
then be tunneled and coupled to the implantable pulse generator, or a new
sterile extension may be used to couple the lead to the implantable pulse
generator.

[0196] Alternatively, when the targeted nerve of passage includes one or
more nerves of the lumbar plexus or sacral plexus, the approach may be
either a posterior (shown in FIG. 16A) or an anterior approach (shown in
FIG. 17A), similar to those used for regional anesthesia of the same
targeted nerve of passage, except that the approach is used for placement
through an introducer of stimulation lead(s) in electrical proximity to
but spaced away from a nerve of passage, and not for regional anesthesia.
Unlike regional anesthesia, the approach to nerves of the lumbar plexus
or sacral plexus do not involve the application of anesthesia to the
nerve, and, when the introducer is withdrawn, the lead(s) may be left
behind to desired stimulation of the target nerve of passage.

[0197] For example, when the targeted nerve of passage includes the
sciatic nerve (see FIG. 18A), the introducer(s) 30 and/or lead(s) 12 may
be directed towards the sciatic nerve using a posterior approach, such as
the transgluteal approach or subgluteal approach, which are both well
described and commonly used in regional anesthesiology (Dalens et al.
1990; Bruelle et al. 1994; di Benedetto et al. 2001; Gaertner et al.
2007).

[0198] This approach allows lead placement near a targeted nerve of
passage with a simple, quick (e.g. less than 10 minutes) outpatient
procedure that may be performed in a standard community-based clinic.
This makes possible widespread use and provides a minimally-invasive
screening test to determine if patients will benefit from the device
before receiving a fully implanted system.

[0199] The landmarks for the transgluteal approach may include the greater
trochanter and the posterior superior iliac spine. The introducer 30 may
be inserted distal (e.g. approximately 2 cm to 6 cm, preferably 4 cm, in
a preferred embodiment) to the midpoint between the greater trochanter
and the posterior iliac spine. As a non-limiting example of patient
positioning, the patient may be in a lateral decubitus position and
tilted slightly forward in a preferred embodiment. The landmarks for the
subgluteal approach may include the greater trochanter and the ischial
tuberosity. The introducer may be inserted distal (e.g. approximately 2
cm to 6 cm, preferably 4 cm, in the preferred embodiment) to the midpoint
between the greater trochanter and the ischial tuberosity.

[0200] For example, when the targeted nerve of passage includes the
femoral nerve (see FIG. 18A), percutaneous leads 12 may be directed
towards the femoral nerve using an anterior approach. The landmarks may
include the inguinal ligament, inguinal crease, and femoral artery. The
subject may be in the supine position with ipsilateral extremity slightly
(approximately 10 to 20 degrees) abducted. The introducer may be inserted
near the femoral crease but below the inguinal crease and approximately 1
cm lateral to the pulse of the femoral artery.

[0201] The size and shape of tissues, such as the buttocks, surrounding
the target nerves may vary across subjects, and the approach may be
modified as needed to accommodate various body sizes and shapes to access
the target nerve.

[0202] In non-amputee patients, introducer placement can be often guided
by muscle response to electrical stimulation, but the muscle response may
not be available in amputees, or may not be available and/or be
unreliable in other situations (e.g., a degenerative diseases or
condition such as diabetes of impaired vascular function in which the
nerves are slowly degenerating, progressing from the periphery, or due to
trauma).

[0203] In these situations, placement may be guided by the individual's
report of stimulus-evoked sensations (paresthesias) as the introducer is
placed during test stimulation. Additionally, the response of remaining
muscles to stimulation may also be used to guide placement of the
introducer and electrode.

[0204] As shown in FIG. 18B, more than a single lead 12 may be placed
around a given nerve of passage, using either an anterior approach (e.g.,
femoral nerve) or a posterior approach (e.g., sciatic nerve). As FIGS.
19A, B, and C show, one or more leads 12 can be placed at different
superior-inferior positions along a nerve of passage and/or along
different nerves of passage.

[0205] As FIGS. 16B (anterior approach, e.g., femoral nerve) and 17B
(posterior approach, e.g., sciatic nerve) show, the lead 12 can be
coupled to an external pulse generator 28 worn, e.g., on a belt 52, for a
trial or temporary stimulation regime. In this arrangement, the lead 12
is covered with a bandage 50, and a surface electrode 54 serves as a
return electrode. The external/percutaneous system shown in FIGS. 16B and
17B may be replaced by an implanted system using an implanted pulse
generator 60 and intramuscular and tunneled leads 62, as shown in FIGS.
16C and 17C, respectively. In this arrangement, the case of the implanted
pulse generator 60A comprises the return electrode.

[0206] D. Stimulation Parameters

[0207] Control of the stimulator and stimulation parameters may be
provided by one or more external controllers. In the case of an external
stimulator, the controller may be integrated with the external
stimulator. The implanted pulse generator external controller (i.e.,
clinical programmer) may be a remote unit that uses RF (Radio Frequency)
wireless telemetry communications (rather than an inductively coupled
telemetry) to control the implanted pulse generator. The external or
implantable pulse generator may use passive charge recovery to generate
the stimulation waveform, regulated voltage (e.g., 10 mV to 20 V), and/or
regulated current (e.g., about 10 mA to about 50 mA). Passive charge
recovery is one method of generating a biphasic, charge-balanced pulse as
desired for tissue stimulation without severe side effects due to a DC
component of the current.

[0208] The neurostimulation pulse may by monophasic, biphasic, and/or
multi-phasic. In the case of the biphasic or multi-phasic pulse, the
pulse may be symmetrical or asymmetrical. Its shape may be rectangular or
exponential or a combination of rectangular and exponential waveforms.
The pulse width of each phase may range between e.g., about 0.1 μsec.
to about 1.0 sec., as non-limiting examples. The preferred
neurostimulation waveform is cathodic stimulation (though anodic will
work), biphasic, and asymmetrical.

[0209] Pulses may be applied in continuous or intermittent trains (i.e.,
the stimulus frequency changes as a function of time). In the case of
intermittent pulses, the on/off duty cycle of pulses may be symmetrical
or asymmetrical, and the duty cycle may be regular and repeatable from
one intermittent burst to the next or the duty cycle of each set of
bursts may vary in a random (or pseudo random) fashion. Varying the
stimulus frequency and/or duty cycle may assist in warding off
habituation because of the stimulus modulation.

[0210] The stimulating frequency may range from e.g., about 1 Hz to about
300 Hz, and the frequency of stimulation may be constant or varying. In
the case of applying stimulation with varying frequencies, the
frequencies may vary in a consistent and repeatable pattern or in a
random (or pseudo random) fashion or a combination of repeatable and
random patterns.

[0211] In a representative embodiment, the stimulator is set to an
intensity (e.g. 1-2 mA (or 0.1-40 mA, or 0.01-200 mA), 100-300 us (or
40-1000 us, or 1-10,000 us)) sufficient to activate the targeted nerve at
some distance X1 (e.g. 1 mm) away (from the targeted nerve of passage).
If the stimulus intensity is too great, it may generate muscle twitch(es)
or contraction(s) sufficient to disrupt correct placement of the lead. If
stimulus intensity is too low, the lead may be advanced too close to the
targeted nerve of passage (beyond the optimal position), possibly leading
to incorrect guidance, nerve damage, mechanically evoked sensation (e.g.
pain and/or paresthesia) and/or muscle contraction (i.e. when the lead
touches the nerve of passage), inability to activate the target nerve
fiber(s) without activating non-target nerve fiber(s), improper
placement, and/or improper anchoring of the lead (e.g. the lead may be
too close to the nerve and no longer able to anchor appropriately in the
muscle tissue).

[0212] In a representative embodiment, the stimulator is set to a
frequency (e.g. 0.5-12 Hz (or 0.1-20 Hz, or 0.05-40 Hz)) low enough to
evoke visible muscle twitches (i.e. non-fused muscle contraction) and/or
muscle contraction(s) of the targeted muscle(s) innervated by the target
nerve of passage, but high enough that that the targeted nerve of passage
will be activated before the lead is advanced beyond the optimal
position.

[0213] As an alternative to using muscle twitch(es) or contraction(s) as
indicator(s) of lead placement (distance from the nerve of passage to
electrode contact), patient sensation could instead be used to indicate
lead location relative to the targeted nerve of passage. Any combination
of stimulus parameters that evoke sensation(s) may be used. Some stimulus
parameters may evoke a more desirable response (e.g. more comfortable
sensation, or a sensation that may be correlated with or specific to the
specific target nerve fiber(s) within the targeted nerve of passage. As
an example, higher frequencies (e.g. 12 Hz, or 4 Hz, or 0.1 Hz) may evoke
sensation(s) or comfortable paresthesia(s) in the region(s) of pain or in
alternate target region(s) (real or phantom) and though they may (or may
not) also evoke muscle contraction(s), the muscle contraction(s) may not
be noticeable (e.g. stimulus intensity may not be sufficient to evoke a
contraction or a twitch from the present lead location or stimulus
intensity may be sufficient to evoke contraction but the muscle
contraction is fused (and no longer visually twitching), making it
difficult to observe visually, unless EMG is used). To take advantage of
both potential indicator responses (muscle twitch and patient sensation),
higher frequencies may be applied intermittently (at lower frequencies),
where the higher frequencies (e.g. 20-120 Hz, or 12-200 Hz) would
normally caused fused muscle contraction if they were applied
continuously but they are applied at an intermittent frequency (e.g.
0.5-4 Hz, or 0.1-11 Hz) that is low enough to allow the muscle to relax
during the gaps between the bursts of stimulation, making it easier to
visualize while still generating patient sensation at a higher frequency,
allowing both muscle twitch and patient sensation to be used
simultaneously as indicators of lead location relative to the targeted
nerve of passage.

[0214] While stimulation is being applied, the lead (non-limiting examples
of the lead could include a single or multi-contact electrode that is
designed for temporary (percutaneous) or long-term (implant) use or a
needle electrode (used for in-office testing only)) may be advanced (e.g.
slowly advanced) towards the targeted nerve of passage until the desired
indicator response (e.g. muscle twitch, muscle contraction, patient
sensation, and/or some combination) is obtained. The intensity may then
be decreased (e.g. gradually decreased) as the lead is advanced (e.g.
advanced slowly) closer to the targeted nerve until the desired indicator
response(s) may be obtained at smaller intensity(ies) within a target
range (e.g. 0.1-1.0 mA (or 0.09-39 mA, or 0.009-199 mA), 100-300 us (or
40-1000 us, or 1-10,000 us)) at some distance X2 (e.g. X2 mm, where
X2<X1, and (as a non-limiting example) X1 may be multiple times larger
than X2, such as X1≧2*X2, or X1≧5*X2, or X1≧20*X2)
spaced from the target nerve.

[0215] In preferred embodiments of the invention, the electrode may be
placed and anchored at about 1 millimeter to about 100 millimeters spaced
from the target nerve, more preferably from about 1 millimeter to about
50 millimeters spaced from the target nerve. The electrode spacing from a
targeted nerve may depend on various factors, and similar stimulation
settings may invoke different responses even if spaced at similar
distances. Thus, electrode spacing from the nerve may be about 10 to
about 20 millimeters for one target nerve at a given stimulation
intensity while the spacing may be about 20 to about 40 millimeters for a
second target nerve at the same stimulation intensity.

[0216] If specific response(s) (e.g. desired response(s) and/or undesired
response(s)) can be obtained at a range of intensities that are too low,
then the lead may be located in a non-optimal location (e.g. too close to
the target nerve(s)). Non-limiting examples of ranges of intensities that
may be considered too low include those that are a fraction (e.g.
<2/3, or <1/5, or < 1/10) of the intensities that obtained the
desired response(s) at X1.

[0217] The preferred stimulus intensities are a function of many
variables, are meant to serve as non-limiting examples only, and may need
to be scaled accordingly. As an example, if electrode shape, geometry, or
surface area were to change, then the stimulus intensities may need to
change appropriately. For example, if the intensities were calculated for
a lead with an electrode surface area of approximately 20 mm2, then
they may need to be scaled down accordingly to be used with a lead with
an electrode surface area of 0.2 mm2 because a decrease in
stimulating surface area may increase the current density, increasing the
potential to activate excitable tissue (e.g. target and non-target
nerve(s) and/or fiber(s)). Alternatively, if the intensities were
calculated for a lead with an electrode surface area of approximately 0.2
mm2, then the intensities may need to be scaled up accordingly to be
used with a lead with an electrode surface area of 20 mm2.
Alternatively, stimulus intensities may need to be scaled to account for
variations in electrode shape or geometry (between or among electrodes)
to compensate for any resulting variations in current density. In a
non-limiting example, the electrode contact surface area may be 0.1-20
mm2, 0.01-40 mm2, or 0.001-200 mm2. In a non-limiting
example, the electrode contact configuration may include one or more of
the following characteristics: cylindrical, conical, spherical,
hemispherical, circular, triangular, trapezoidal, raised (or elevated),
depressed (or recessed), flat, and/or borders and/or contours that are
continuous, intermittent (or interrupted), and/or undulating.

[0218] Stimulus intensities may need to be scaled to account for
biological factors, including but not limited to patient body size,
weight, mass, habitus, age, and/or neurological condition(s). As a
non-limiting example, patients that are older, have a higher body-mass
index (BMI), and/or neuropathy (e.g. due to diabetes) may need to have
stimulus intensities scaled higher (or lower) accordingly (Bigeleisen et
al 2009).

[0219] As mentioned above, if the lead is too far away from the targeted
nerve of passage, then stimulation may be unable to evoke the desired
response (e.g. muscle contraction(s), comfortable sensation(s) (or
paresthesia(s)), and/or pain relief) in the desired region(s) at the
desired stimulus intensity(ies). If the lead is too close to the targeted
nerve of passage, then stimulation may be unable to evoke the desired
response(s) (e.g. muscle contraction(s), comfortable sensation(s) (or
paresthesia(s)), and/or pain relief) in the desired region(s) at the
desired stimulus intensity(ies) without evoking undesirable response(s)
(e.g. unwanted and/or painful muscle contraction(s), sensation(s) (or
paresthesia(s)), increase in pain, and/or generation of additional pain
in related or unrelated area(s)). In some cases, it may difficult to
locate the optimal lead placement (or distance from the targeted nerve of
passage and/or it may be desirable to increase the range stimulus
intensities that evoke the desired response(s) without evoking the
undesired response(s) so alternative stimulus waveforms and/or
combinations of leads and/or electrode contacts may be used. A
non-limiting example of alternative stimulus waveforms may include the
use of a pre-pulse to increase the excitability of the target fiber(s)
and/or decrease the excitability of the non-target fiber(s).

[0220] Those skilled in the art will recognize that, for simplicity and
clarity, the full structure and operation of all devices and processes
suitable for use with the present invention is not being depicted or
described herein. Instead, only so much of an implantable pulse generator
and supporting hardware as is unique to the present invention or
necessary for an understanding of the present invention is depicted and
described. The remainder of the construction and operation of the IPGs
described herein may conform to any of the various current
implementations and practices known in the art.

III. REPRESENTATIVE INDICATIONS FOR CHRONIC OR TEMPORARY PAIN THERAPY

[0221] Localized pain in any area of the body (e.g., the skin, bone,
joint, or muscle) can be treated with by applying electrical stimulation
to a muscle in electrical contact with but spaced from a targeted nerve
of passage. Electrical stimulation of nerves of passage works by
interfering with or blocking pain signals from reaching the brain, as
FIG. 10 schematically shows.

[0222] Many pain indications can be treated by nerves of passage
stimulation.

[0223] Pain in the leg may occur in areas such as the thigh, calf, hip,
shin, knee, foot, ankle, and toes. There may be multiple causes of leg
pain, including but not limited to injury (e.g. traumatic) to a muscle,
joint, tendon, ligament or bone; muscle or ligament damage; ligament
sprain, muscle or tendon strain; disease or disorders; phlebitis,
swelling, or inflammation; claudication; insufficient blood flow into
(arterial insufficiency) or away from (venous insufficiency) a part of
the leg or foot; ischemia; peripheral artery disease; arthritis; tumor
(malignant or benign); peripheral neuropathy; diabetic peripheral
neuropathy; and post herpetic neuralgia.

[0224] For example, peripheral artery disease can cause pain (especially
during activity such as walking or running) because the effective
narrowing of the arteries leads to a decrease in the supply of blood and
therefore in the supply of nutrients such as oxygen to the active
muscles, leading to pain. This phenomenon can occur in almost in area of
the body but may be more common in the leg, especially parts of the lower
leg, such as the calf. Activity is not always required to elicit pain and
pain may occur even at rest (without activity or exercise). Nerve
entrapment, compression, injury or other types of damage may cause pain
in the areas innervated by the damaged nerve, which can lead to referred
pain in an area distal to the injury.

[0225] The femoral nerve has anterior branches (intermediate cutaneous
nerve and medial cutaneous nerve) and posterior branches. The saphenous
nerve (branch of the femoral nerve) provides cutaneous (skin) sensation
in the medial leg. Other branches of the femoral nerve innervate
structures (such as muscles, joints, and other tissues) in the thigh and
around the hip and knee joints. As an example, branches of the femoral
nerve innervate the hip joint, knee joint, and the four parts of the
Quadriceps femoris (muscle): Rectus femoris (in the middle of the thigh)
originates on the ilium and covers most of the other three quadriceps
muscles. Under (or deep to) the rectus femoris are the other 3 of the
quadriceps muscles, which originate from the body of the femur. Vastus
lateralis (on the outer side of the thigh) is on the lateral side of the
femur. Vastus medialis (on the inner part thigh) is on the medial side of
the femur. Vastus intermedius (on the top or front of the thigh) lies
between vastus lateralis and vastus medialis on the front of the femur.
Braches of the femoral nerve often innervate the pectineus and Sartorius
muscles arises.

[0226] The sciatic nerve has branches that innervate the biceps femoris,
semitendinosus, semimembranosus, and adductor magnus muscles. 2 major
branches of the sciatic nerve are the tibial and common peroneal nerves
that innervate much of the lower leg (around and below the knee). For
example, the tibial nerve innervates the gastrocnemius, popliteus, soleus
and plantaris muscles and the knee joint. Most of the foot is innervated
by the tibial and peroneal nerve.

[0227] For example, claudication pain (occurring in the calf muscle) could
be treated by nerves of passage stimulation by placing the lead in the
gluteus muscle near the sciatic nerve, which passes by the gluteus muscle
on its way to innervate the calf muscle.

[0228] In general pain due to poor blood flow to an area or damage to an
area can be relieved by stimulation of the nerve innervating that area.
Since diabetic neuropathy typically leads to pain in the more distal
areas (toes/foot), stimulation of the sciatic nerve can relive that pain.
Pain in the skin of the medial (inner) calf can be relieved by
stimulation of the femoral nerve. Pain in the front of the thigh (quad's)
can be relieved by stimulation of the femoral nerve. If pain overlaps
more than one area, stimulation of multiple nerves (e.g., sciatic and
femoral nerves) can be beneficial.

[0229] Stimulation of the intercostal nerves (originating from the
Thoracic nerve roots (T1-12)) can relieve pain in regions innervated by
the intercostal nerves such as pain from intercostal neuralgia or post
herpetic neuralgia. The pain may be confined to the area (e.g. dermatomic
area) innervated by 1 or 2 nerves and may follow outbreak (and recovery)
of herpes zoster. The pain may last up to several months or years in some
patients and may be caused by nerve irritation or damage due to herpes
zoster.

[0230] Amputation (phantom) pain can also be treated by nerves of passage
stimulation. For example, upper extremity stimulation of spinal nerves
passing through the brachial plexus can relive phantom pain that results
from amputation of an upper limb. Likewise, lower extremity stimulation
of spinal nerves passing through the lumber plexus sacral plexus (e.g.,
the sciatic nerve or the femoral nerve) can relive phantom pain that
results from amputation of a lower limb.

IV. CONCLUSION

[0231] In "nerves of passage" stimulation, the lead is placed in a muscle
by which the targeted nerve passes, but stimulation actually relieves
pain that is felt distal (downstream) from where the lead is placed. In
"nerves of passage" stimulation, the lead can be placed in a muscle that
is conveniently located near a nerve trunk that passes by the lead on the
way to the painful area. The key is that the lead is placed in a muscle
that is not the target (painful) muscle, but rather a muscle that is
proximal (upstream) from the painful region because the proximal muscle
is a more convenient and useful location to place the lead.

[0232] The advantages of nerves of passage stimulation can be recognized
by anesthesiologists who are used to placing needles deeper in the muscle
near nerves of passage Anesthesiologists are accustomed to placing
needles proximal (upstream) from the areas of pain to numb the areas
downstream. Anesthesiologists already use ultrasound and the
electro-location techniques that would be needed to place leads to access
nerves of passage.

[0233] Nerves of passage stimulation provides stimulation-generated
paresthesias (that ideally overlap with the area of pain) but does not
require evoking a muscle contraction to place the lead correctly. The
target regions in which pain is felt and which are targeted for
generation of paresthesia are not the same region in which the lead is
placed. This is an advantage because physicians (e.g. anesthesiologists)
who will typically be placing the lead are accustomed to using
paresthesias (sensory feedback description of from the patient) to guide
lead placement and tuning of stimulation parameters.

[0234] Evoking muscle contraction with stimulation is not required for
pain relief or lead location. Evoking muscle contraction with stimulation
may help in relieving pain or placing the lead, but it is not required.
It is an advantage that muscle contraction is not required because it
allows this method to treat pains in which muscle contraction cannot be
evoked (e.g. in the case of amputation pain in which the target area has
been amputated and is no longer physically present or other cases of
nerve damage either due to a degenerative diseases or conditions such as
diabetes of impaired vascular function, in which the nerves are slowly
degenerating, progressing from the periphery, or due to trauma.

[0235] In nerves of passage stimulation, the primary targeted pain area is
distal to the lead, meaning that the lead is in between the major area in
which pain (e.g. the worst, most troubling, or most interfering pain) is
felt and the center of the body (e.g. the spinal cord)).

[0236] Imaging (e.g., ultrasound or an alternate imaging technique, e.g.
fluoroscopy) may be used to improve lead placement near nerves of
passage. Ultrasound may improve lead placement in the form of increasing
the total speed of the procedure (shortening the procedure's duration,
not necessarily increasing the speed at which the lead is advanced in the
form of locating the lead in a more optimal location (to improve
recruitment of the target fibers in the target nerve and minimize
recruitment of non-target fibers (e.g. c fibers, other non-target sensory
fibers, motor fibers, etc.) in either the target nerve and/or in
non-target nerve(s); in the form of minimizing risk and/or damage to the
patient during placement of the lead (by avoiding blood vessels, organs,
bones, ligaments, tendons, lymphatic vessels, &/or other structures) that
may be damaged. One reason that imaging may be useful is that some nerves
of passage are (but do not have to be) located relatively deeply.
Fluoroscopy is not required to place the lead. It may help, but it is not
required. Imaging is not required.

[0237] The patient is not required to give verbal, written, or other type
of feedback or indication of what they feel as the lead is being advanced
towards the nerve of passage if muscle contraction or imaging is used to
guide lead placement, but patient feedback during lead advancement may
improve lead placement in some patients, especially in cases where
(distal) muscle contraction cannot be used to confirm correct lead
placement (e.g. amputees, nerve injury, nerve degeneration (e.g. due to
vascular dysfunction, diabetes, etc), stimulation of a sensory nerve).
The patient may indicate sensations during tuning of stimulus intensity
(but this is a different step in the process and is performed after the
lead has been correctly positioned). As non-limiting examples, those
sensations reported by the patient may include first sensation (minimum
stimulus intensity that evokes a sensation), level of comfort, maximum
tolerable sensation, pain, qualities &/or descriptions of the sensations.

[0238] The region in which the patient perceives stimulation-induced
sensations and/or paresthesias may be an important indicator of the
potential success of the therapy (e.g. used in screening potential
candidates), and the stimulation parameters (including but not limited to
lead location) may be adjusted so that the region in which paresthesias
are perceived overlaps with the region of pain.

[0239] As an alternative to using perception of stimulation induced
sensations and/or paresthesia, the level of pain and/or change in the
intensity of pain during and/or due to stimulation may be used to adjust
stimulation parameters (including but not limited to lead location).

[0240] The foregoing is considered as illustrative only of the principles
of the invention. Furthermore, since numerous modifications and changes
will readily occur to those skilled in the art, it is not desired to
limit the invention to the exact construction and operation shown and
described. While the preferred embodiment has been described, the details
may be changed without departing from the invention.